The present invention relates generally to reinforced structures, and more particularly, to improved reinforced concrete foundation structures used in the erection of electric power, transmission towers, light poles, and other structures wherein a load is intended to be supported at great height above the ground.
At present, it is the practice to mount light poles, highline towers, and the like, on foundations which comprise generally cylindrical reinforced concrete structures extending well below the ground, a distance which is selected in relation to the height of the supported structure which, in many cases, aggregates 40, 60, or 80 feet by way of example. The tower or pole is supported on a flat plate or ring, having a plurality of fastener receiving openings therein. The pole extends upwardly from this ring which is formed integrally with, or attached by welding to a part of the above ground structure. When the pole or tower element is disposed over the foundation member, pieces of threaded rod which are embedded in the foundation member extend upwardly through the openings in the ring. These are indexed with the holes and the structure is mounted by attaching nuts to the ends of the threaded rods and tightening them in position. This holds the tower, pole or other structure down onto the foundation member. The foundation member consists of a caselike, or cylinderlike, concrete structure wherein the reinforcing rods or bars extend substantially the entire length or depth thereof. Because the poles, towers, or the like, are subjected to considerable stress, it has been a requirement that the threaded rod, which acts both as a mounting means for the pole and as a reinforcing bar for the concrete, be made from a heat treated, high tensile strength steel material. This is because it is desired that the supported structure not fail at the connection as might be the case if a soft, relatively low grade steel were used. In the past, before standards were adopted which call for the use of high quality heat treated, high tensile strength rod material, there were occassional failures in use which resulted from breaking of the rod at the fasteners. This failure was usually due to work hardening of material as the threads were cut or rolled on the rod, or to the fact that the threaded rod, as manufactured, had faults or impurities therein, or for other reasons. Consequently, high strength heat treated materialwas specified to minimize the risk of breakage at the point wherein the maximum stress was concentrated, namely, at the top of the foundation, where the pole, or tower structure was mounted to the foundation. In current practice, as a result of adopting standards referred to above, it has been customary to use high tensile strength heat treated reinforcing rods running the entire length of the casing or column, in this case, such depth reaching as much as 80 feet. Since such material is highly expensive, the requirement for the use of high quality material has greatly increased the cost of this type foundation structure and a need has arisen for the design of a foundation structure of this type which will meet the strength requirements and which can be built at a substantially smaller cost.
It is a general object, therefore, of the present invention to provide an improved foundation structure of the type which is particularly adapted for supporting electrical transmission towers, light poles and similar structures which rise to a substantial height above the foundation and exert considerable tensile and shear stress at the base where they are joined to the foundation structure.
It is a more specific object of the invention to provide an improved method of constructing a foundation structure of the type which is employed for supporting relatively high electric line poles, power transmission towers, or similar structures, where the foundation structure may be constructed on the site and where it may be capable of exerting the high tensile and shear strength necessary to maintain the pole or tower structure in its upright position under adverse conditions.
A still more specific object of the invention is to provide an earth pile anchorage structure which will serve as a reinforced load bearing column wherein a composite reinforcing bar is combined with concrete, which reinforcing bar is formed by connecting an upper rod section of heat treated material to a lower rod section of good grade reinforcing steel bar stock by means of a specially designed coupler unit.
Another object of the invention is to provide a concrete column for supporting a pole, or similar structure, which is reinforced with one or more composite reinforcing rods comprised of a high tensile strength steel section, an ordinary steel reinforcing rod section, and a connector which serves to couple the steel sections together, which is easily assembled and which includes an inspection opening to insure that assembly is completed, with the composite rod structure or structures being adapted to be held in place by fixtures in the opening of a vertical bore of suitable size into which concrete may be poured to create a structure which is capable of supporting the pole and withstanding shearing and bending forces to which the upper portion may be subjected, and the tensile forces which will be distributed throughout the height of the column.
Still antoher object of the invention is to provide a reinforced concrete column arrangement for supporting a tower or pole structure which has the strength required by current specifications for such structures and which can be fabricated at lower cost than currently available column arrangements.
A further object is to provide a composite reinforcing member for a reinforced foundation structure which consists of a length of lower grade steel material having a threaded end portion, a length of higher grade material which is preferably threaded throughout and a coupler having an inspection opening insuring that both members are fully inserted therein, with a plurality of the reinforcing members being arranged as reinforcing bars extending longitudinally of the foundation structure.
To this end the invention comprises a method of forming a reinforced structure which is adapted to be employed as a foundation column for a high rising tower or polelike structure wherein one or more reinforcing rod assemblies are set in concrete, which rod assemblies comprise a lower rod section of conventional bar stock reinforcing material which is of substantial length relative to the column height joined by a coupling member to an upper rod section of substantially lesser length than the lower rod section and of a high strength material capable of withstanding relatively high shearing and bending forces.
The foregoing and other objects and advantages of the invention will be best understood when reference is made to the accompanying description of the preferred form of the invention which is set forth herein, by way of example, and shown in the drawings wherein like reference numerals indicate corresponding parts throughout.